In a digital multiplexing apparatus and a digital demultiplexing apparatus adapted to multiple rates, it has been possible to perform digital demultiplexing and digital multiplexing of signals in various band widths by combining a sub-filter and Fourier transform (or fast Fourier transform: FFT) means. Technologies concerning the digital multiplexing apparatus and the digital demultiplexing apparatus adapted to multiple rates are disclosed in Patent Literature 1 and a Non-Patent Literature 1 below.